A. Field of the Invention
The present invention relates generally to compositions and methods that can be used to stabilize vitamin C.
B. Description of Related Art
Vitamin C is an antioxidant that can benefit the skin when applied topically. Topical use of vitamin C may supplement sunscreen protection and provide additional anticarcinogenic protection. (Pinnel, 2003; Humbert 2001). Topical application of vitamin C can provide additional protection against sun damage (Lin et al., 2003). Vitamin C has been shown to result in clinically visible and statistically significant improvement in wrinkling in humans (Fitzpatrick et al., 2002).
Although topical vitamin C application can benefit the appearance and health of skin, problems limit the use of vitamin C in cosmetic compositions. In particular, vitamin C can be difficult to stabilize in topical compositions. For example, U.S. Pat. No. 2,400,171 discloses the conversion of ascorbic acid to its calcium or zinc salt to maintain stable aqueous solutions. U.S. Pat. No. 6,146,664 explains that the difficulties in preparing a stable vitamin C composition is because the ascorbic acid is an α-ketolactone having a double bond between the second and third carbon atoms of the structure. This combined with the hydroxyl groups at the second and third carbon atoms of vitamin C make vitamin C a fairly strong reducing agent. In aqueous media, therefore, vitamin C looses its beneficial effects because of degradation or reaction with other compounds.